Filter



Sept. 12, 1961 M. o. SCHUR ETAL FILTER Filed Dec. 23. 1953 INVENTORS MILTON o. SGHUR BY JAMES c. RICKARDS United States Patent 2,999,503 FILTER Milton 0. Schur, Asheville, and James C. Rickards, Breuard, N.C., assignors, by mesne assignments, to Olin Mathieson Chemical Corporation, a corporation of Virginia Filed Dec. 23, 1953, Ser. No. 400,072 2 Claims. (Cl. 131-208) This invention relates generally to tobacco smoking devices and more particularly to a novel filter therefor and to a method for making the same.

Cigarettes and similar smoking devices have been provided, heretofore, with a filter for the tobacco smoke. Ordinarily, such filters have been formed by enclosing within a wrapper wound or folded paper having longitudinal channels between the various plies of paper. It has been proposed, for example by Davidson in US. Patent 2,001,709 and by Edwards in U.S. Patent 2,160,- 201, that the paper utilized in such filters be creped in a direction parallel to the longitudinal axis of the filter. It also has been proposed to intersperse alternate layers of a flulfy asbestos or cotton material between convolutions of crepe paper to form a filter having improved filtration characteristics. In still another type of filter, a preformed strip or rod of wadding of proper diameter is cut to length and is inserted into the end of a cigarette wrapper to serve as a filter. None of these heretofore proposed filters have been entirely suitable, however, some of them being substantially ineffective in retaining undesirable constituents of tobacco smoke while others tend to impede the fiow of smoke to an objectionable extent and to offer difficulty in manufacture.

It is an object of this invention to provide smoking devices with a filter devoid of the foregoing disadvantages. Another object of the invention is to provide a filter for tobacco smoke having improved filtration characteristics. A more specific object of the invention is to Provide a filter for smoking devices which retains undesirable constituents of tobacco smoke and does not seriously impair the smoking characteristics of the device. A still further object of the invention is to provide a method for making an improved filter for tobacco smoking devices. Still another object is to provide a cigarette with a filter of simple manufacture.

Other objects will become apparent from the following description with reference to the accompanying drawing in which:

FIGURE 1 is a diagrammatic perspective view of one type of apapratus suitable for forming an embodiment of this invention;

FIGURE 2 is a perspective view of one embodiment of the invention attached to a cigarette; and

FIGURE 3 is a diagrammatic view of apparatus suitable for forming another embodiment of the invention.

Generally speaking, the foregoing objects and others are achieved in accordance with this invention by enclosing within a wrapper a myriad of layers of paper formed from paper weighing not more than about 25 grams per square meter. The multitudinous layers of paper substantially fill the wrapper but leave a maze of passageways between the layers which extend tortuously through the filter in a longitudinal direction. Preferably, the filler, that is, the plurality of layers, or folds, of paper within the wrapper, should weigh from about 0.1 gram to about 0.3 gram per cubic centimeter. Best results are obtained if a pliant paper such as crepe paper or other paper having a rough surface such as embossed paper is utilized, particularly if the weight thereof is between about 16 grams and 25 grams per square meter. Ordinarily papers weighing from about 7 grams to 25 grams 'ice per square meter before creping and before crumpling are preferred.

It has been found advantageous in the case of cigarettes containing some blends of tobacco to use highly purified pulp, for eiiample, the so-called high alpha cellulose pulps of commerce, in the manufacture of the paper for the filtering medium in our filter plug. In any event, the paper should be free from contaminants, whether naturally occurring or otherwise.

The paper must be crumpled by being worked mechanically. If a light weight paper of less than about 16 grams per square meter is utilized good filtration characteristics are obtained if the only crumpling is done by the cone of a cigarette forming machine While the paper is being placed within the wrapper, as will be described in more detail hereinafter. With the heavier weight papers of the invention and preferably even with the lighter weight papers, however, the paper is crumpled by a process in addition to the one by which it is inserted in the wrapper. Any crumpling process which forms a multitude of irregularly extending and irregularly spaced rumples may be utilized to advantage, but best results are obtained if the paper is crumpled by a process wherein it is compressed in a plurality of steps with a time interval interspersed between each step for the paper to spring back or expand at least partially. A result similar to that desired is obtained by wadding or crushing a sheet of paper in the hand. Paper crumpled in this way is much softer and is inherently more pliant than before such mechanical working, probably because the bond between fibers has been loosened or the fibers have been partially pulled apart. A similar result is also obtained if the paper is heavily embossed before it is fed to the forming machine. Indeed, embossing is one of the preferred methods of preconditioning the paper for use in the manufacture of cigarette filters. In general, the greater the weight of the paper utilized, the more crumpling or other softening means required for optimum results.

A particularly advantageous method of crumpling the paper is to pull one or more sheets, ribbons or webs thereof through a series of orifices, each on'fice having lesser dimensions than the preceding one. By way of example a set of three circular orifices arranged one after the other in the order of decreasing diameter in the ratio of about 0.25, 0.22, and 0.20 has been found admirably suited for the purpose. A greater or lesser num ber of orifices may be advisable with some papers, however, and the opening may be square, oval or of other shape adapted to crumple and to compress the paper as it is pulled therethrough. The tortuous passageways through the filter resulting from forming it from the crumpled paper insure that the smoke will impinge against the surface thereof as it passes through the filter.

The filtering characteristics of a filter are further improved if substantially unfibrillated paper is utilized in forming the labyrinthal structure. As is well known in the paper making art, fibrillation is the first step in the conversion of pulp into paper. The more the cellulose fibers are fibrillated, that is, the longer they are subjected to the action of a beater, the greater the surface area of the fibrils and the tighter will be the interlock formed between the fibrils when they are formed into a sheet. Paper which has been formed from only moderately fibrillated or unfibrillated cellulose has an open. structure which is substantially porous and absorbent.

It has been found that the filter of this invention can be formed on a conventional cigarette wrapping machine embodying modifications to adapt it for feeding the paper into the forming cone of the machine and for enclosing the layers of paper within the Wrapper. The multitude of layers of paper may be formed from a single sheet of paper or from a plurality of sheets. When the heavier papers weighing about 16 grams or more per square meter are utilized, it has been found that even distribution of the layers within the wrapper is most easily approached if a plurality of sheets which have been separately crumpled before they are compressed together by the forming cone are utilized. Three separately crumpled sheets weighing about 16 grams per square meter compressed together in the forming cone of a cigarette machine make an advantageous filter.

If crepe paper is utilized best results are obtained if the direction of creping is transverse to the direction of flow of smoke through the filter. Preferably, the percentage crepe in the paper should be within the range of from about 8 percent to about 60 percent. In other words, a sheet about 10 inches long is reduced to a length in the range of from about 9.2 inches to about 4 inches when creped. The paper used to form the labyrinthal filler may be carried by the wrapper as it is pulled through the forming cone of the cigarette making machine. The resulting plug may be cut into any convenient length and the intermediate product may be later cut to the required length for use in the smoking device. When so desired, paper impregnated with a wet strengthening agent, for example melamine formaldehyde resin, urea formaldehyde resin, viscose, etc., may be utilized in order that the filter tip may resist disintegration by moisture.

The filter provided by this invention has been found to be effective in retaining the undesirable constituents of tobacco smoke without seriously impairing the smoking characteristics of the smoking device by grossly impeding the flow of smoke through the filter. A filter having a density Within the preferred limits set forth elsewhere herein and formed in accordance with this invention to have thevarious layers of paper forming the labyrinth of passageways therebetween substantially uniformly distributed throughout the cross-sectional area of the filter ordinarily need impose a resistance to the passage of smoke no greater than that equivalent to a loss of head of about centimeters of water when the smoke is travelling through the filter at a rate of about 18 cubic centimeters per second. This is an important characteristic of the filter because the heretofore available filters which removed as much as about 50 percent of the tars, etc. from the tobacco smoke impose a much greater resistance to the flow of smoke therethrough. In fact, the resistance of such filters is so great the average tobacco smoker will not tolerate it.

In order better to clarify and further describe the invention the following are embodiments thereof Referring to FIGURE 1 which is a diagrammatic perspective view of one type of machine suitable for forming 'a filter in accordance with this invention, a sheet 1(a) of conventional cigarette or other paper suitable for a filter Wrapper is pulled from roll 4 by any suitable means such as by an endless belt 23 through the forming cone 3 of a conventional cigarette making machine. Before sheet 1(a) enters the forming cone 3, however, a plurality of layers of papers 2 suitable forthe filler are pulled from roll 5 and are laid thereon and are carried thereby through the forming cone 3. Sheet 1(a) is convolutely wound as it passes through the cone to form wrapper 1. Edge 7 of sheet 1(a) remains substantially perpendicular during the early stages of this process. Paper 2 in this particular embodiment is composed of thirty-eight layers of crepe paper out from thirty-eight sheets of paper of substantially identical weight each of a weight about 9 grams per square meter as measured on samples of the paper with the crepe pulled out. The direction of creping is transverse the direction of travel of the paper. Ribbon 2 is about /2 inch wide and the width of wrapper 1 is about 1.2 inch. As wrapper 1 is wound into a tube, the plurality of plies or layers of paper 2 are gathered together and are compressed therein leaving a maze of tortuous passageways 8 (FIGURE 2) extending longitudinally therethrough. A suitable gum adhesive is applied to edge 7 by applicator wheel 9 and edge 7 is folded to overlap edge 11 by means of the final forming cone 6. The overlapped edges 7 and 11 are tightly bound together as heated roller 10 passes thereover and removes water and any other liquids from the adhesive. Rotary cutter 12 severs the resulting labyrinth-a1 structure into rods such as 13. This rod 13 is later cut to a length suitable for a cigarette filter tip 17 and is enclosed in the cigarette wrapper 14, as illustrated in FIGURE 2, by conventional methods as the wrapper 14 is wound around the tobacco 15 to form cigarette 16. The density of the filter is about 0.15 gram per cubic centimeter.

In another embodiment of the invention, three webs of embossed paper 18, 19 and 20 illustrated in FIGURE 3 each 7 /2 inches wide and each weighing about 20 grams per square meter are separately crumpled before they are labyrinthed Within a wrapper such as 1 in FIGURE 1. The embossed paper has a waffle-like pattern with about 30 depressions per square inch. As shown digrammatically in FIGURE 3, web 18 is pulled through orifice 22 and then through orifices 25 and 26 in plates 28, 29 and 30 respectively. The diameter of orifices 22, 25 and 26 is about 0.25, 0.22 and 0.20 inch respectively. The plates 28, 29 and 30 are located a sufficient distance apart to permit the crumpled paper web 18 to expand before being crumpled again in a succeeding orifice such as illustrated at 24 and 27. Ordinarily a distance of about 3 to 4 inches between a pair of plates is suflicient. Web 19 is crumpled by pulling it through orifices 31, 32 and 33. The web 19 is allowed to expand as shown at 37 and 38 and the diameter of the orifices 31, 32 and 33 is about 0.25, 0.22 and 0.20 inch, respectively. Web 20 is similarly crumpled by pulling it through orifices 34, 35 and 36 in the resinous plates, the dimensions of the orifices being the same as those of orifices 31, 32 and 33. crumpled webs 18, 19 and 20 are carried by a paper similar to 1(a) of FIGURE 1 which, in turn, is drawn by a conveyor belt 23 through the cone 3 of a cigarette machine where they are gathered together and compressed within a wrapper '1 in substantially the same way as is described with respect to the plurality of plies of paper 2 of the embodiment described in the foregoing. The resulting filter has a density of about 0.2 to 0.25 gram per cubic centimeter.

It has been found that the filters of this invention including those described in the foregoing examples are more efiective for a given resistance to the flow of smoke in retaining constituents of tobacco smoke than any of the heretofore available filters formed from other materials including conventional heavier weight and stiffer crepe paper. In one experimental test, wherein a cigarette having attached thereto a filter about eleven millimeters long and about eight millimeters in diameter similar to the one formed from thirty-eight plies of paper in the foregoing example was smoked in a conventional smoking machine designed to simulate subjective smoking conditions, the filter removed about 50 percent of the undesirable constituents such as tars, etc. from the smoke of a burning cigarette. The loss in head through the filter was equivalent to a column of water about 4.6 centimeters high when the rateof flow of the smoke through the filter was about 18 cubic centimeters per second, a typical rate of flow when a'cigarette is smoked. In a similar test, a filter similar to one formed from webs 18, 19 and 20, as described, removed about 50 percent of the undesirable constituents from the tobacco smoke. The drag or loss in head through the filter was about 3.8 centimeters. A commercially available filter formed from conventional crepe paper weighing about 42 grams per square meter before creping and about grams per square meter after creping was tested under substantially identical conditions. The percentage crepe was about 62 percent. The filter was about 11 millimeters long and the various plies of longitudinally creped paper were closely cornpressed together within a cigarette paper wrapper to provide longitudinal channels for passage of the smoke through the filter. This filter removed substantially none of the tars from the smoke drawn therethrough.

The foregoing embodiments have been described in detail only for the purpose of illustrating the invention and many modifications may be made therein by those skilled in the art without departing from the spirit of the invention. For example, several sheets of paper of many plies may be utilized instead of the three single sheets 18, 19 and 20. A separate series of orifice plates may be provided for each sheet to be crumpled and the diameter of the orifice will vary with the type of paper utilized. Any diameter which crumples the paper is suitable but best results are obtained if the smallest diameter permissible Without tearing is used. The pattern embossed into the paper may be irregular rather than regular as described above. Any suitable adhesive may be utilized for binding the overlapping edges of the wrapper of the filter and the intermediate partial uncrumpling or expansion step between crumpling steps may be omitted in some instances.

Although the filter has been shown attached to a cigarette, filters suitable for other smoking devices such as cigarette holders, cigars, pipes and the like can be formed in accordance with this invention. The intermediate product 13 can be cut to any suitable length for such devices.

' A wrapper weighing about 20 grams per square inch is suitable; however a wrapper weighing from about 40 grams per square meter to about 60 grams per square meter is preferred when it is desired to impart extra stiffness to the filter to prevent harmful distortion thereof by ordinary handling.

Having described the invention, What is claimed and desired to secure by Letters Patent is:

l. A filter for smoking devices comprising a wrapper and enclosed within the wrapper a filling of crumpled and gathered paper sheet, said sheet initially weighing about 7 to 25 grams per square meter and said filling being substantially uniformly distributed within the said wrapper at a density of about 0.1 to 0.3 gram per cubic centimeter and having a multitude of generally Iongitudinal tortuous passageways therethrough, said paper having been substantially softened prior to enclosure within the said wrapper by random mechanical working thereof until the vast majority of its fibers have been partially pulled apart at random locations therein.

2. A filter for smoking devices comprising a wrapper and enclosed within the wrapper a filling of crumpled and gathered paper sheet, said sheet initially weighing about 7 to 25 grams per square meter and said filling being substantially uniformly distributed Within the said wrapper at a density of about 0.1 to 0.3 gram per cubic centimeter and having a multitude of generally longitudinal tortuous passageways therethrough, said paper having been substantially softened prior to enclosure within the said wrapper by random mechanical working thereof until the bond between substantially all of its fibers has been loosened at random locations therein.

References Cited in the file of this patent UNITED STATES PATENTS 598,086 Hannan Feb. 1, 1898 1,980,563 Walker Nov. 13, 1934 2,033,867 Segal Mar. 10, 1936 2,035,398 Muller Mar. 24, 1936 2,039,298 Davidson May 5, 1936 2,064,239 Aivaz Dec. 15, 1936 2,164,702 Davidson July 4, 1939 2,221,443 Davidson Nov. 12, 1940 2,372,437 Lathrop et al Mar. :27, 1945 2,497,074 Dudley et a1. Feb. 14, 1950 2,668,544 Davidson Feb. 9, 1954 2,708,982 McGufi May 24, 1955 FOREIGN PATENTS 448,889 Italy Nov. 25, 1948 OTHER REFERENCES Stephenson: Pulp and Paper Manufacture," vol. 2, 1st ed. (1950), published by McGraw-Hill Book Co. Inc., N. Y. 587 pp., page 193 especially cited. 

